EP0984569A1 - Satellite broadcasting system and broadcasting satellite - Google Patents
Satellite broadcasting system and broadcasting satellite Download PDFInfo
- Publication number
- EP0984569A1 EP0984569A1 EP98921890A EP98921890A EP0984569A1 EP 0984569 A1 EP0984569 A1 EP 0984569A1 EP 98921890 A EP98921890 A EP 98921890A EP 98921890 A EP98921890 A EP 98921890A EP 0984569 A1 EP0984569 A1 EP 0984569A1
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- European Patent Office
- Prior art keywords
- broadcasting
- signal
- communication channels
- satellite
- transmitted
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/204—Multiple access
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
- H04H20/65—Arrangements characterised by transmission systems for broadcast
- H04H20/71—Wireless systems
- H04H20/74—Wireless systems of satellite networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/18523—Satellite systems for providing broadcast service to terrestrial stations, i.e. broadcast satellite service
Definitions
- This invention relates to a satellite broadcasting system for providing broadcasting of images, voices, data, etc., using a broadcasting satellite located in a stationary orbit above the equator, and also to the broadcasting satellite used for the satellite broadcasting.
- satellite broadcasting In accordance with the demand for various kinds of broadcasting services and with the development of communication techniques, satellite broadcasting has been started in addition to ground broadcasting. Since satellite broadcasting can provide services in a wide area without establishing a large-scale infrastructure, attention is now paid to it as a medium that can satisfy many needs.
- BS Broadcasting Satellite
- CS Common Satellite
- certain transmitting stations collect broadcasting signals of a plurality of channels and multiplex them before transmitting them to an up transmission line leading to the broadcasting satellite.
- the broadcasting satellite converts the frequency of each signal input thereto via the up transmission line, to a value corresponding to a down transmission line to the ground, and performs power amplification of each signal, thereby transmitting each resultant signal to a predetermined service area.
- all broadcasting signals of a plurality of channels are transmitted to the predetermined service area. In other words, broadcasting is always performed only for a single service area.
- a feeder link station is necessary for collecting broadcasting signals of a plurality of channels, and then transmitting them to the up transmission line.
- it is necessary to secure a ground transmission line between the broadcasting station and the feeder link station, which inevitably makes the system complicated.
- a particular feeder link station concentrically performs signal transmission to a broadcasting satellite, and the broadcasting satellite itself only relays signals transmitted from the feeder link station. Accordingly, the system structure is complicated, and the service area is disadvantageously inflexible.
- the present invention has been developed in light of the above, and is aimed at providing a satellite communication system of a simple structure capable of changing the service area for each of broadcasting signals, and also providing a broadcasting satellite that enables the satellite communication system.
- the invention provides a satellite broadcasting system that uses a broadcasting satellite located in a stationary orbit above the equator to provide a user with broadcasting from a plurality of transmitting stations such as broadcasting stations, characterized in that the broadcasting satellite comprises: a reception antenna such as a Ka-band antenna for receiving a signal transmitted via a predetermined up transmission line on which a plurality of communication channels are set; a transmission antenna such as an S-band antenna having a plurality of radiators for emitting transmission beams to a plurality of areas; channel separating means such as a band-pass filter for extracting, from the signal received by the reception antenna, a signal transmitted through each of the plurality of communication channels; and a plurality of signal processing means such as synthesizers, high power amplifiers, etc.
- a reception antenna such as a Ka-band antenna for receiving a signal transmitted via a predetermined up transmission line on which a plurality of communication channels are set
- a transmission antenna such as an S-band antenna having a plurality of radiator
- each of the plurality of transmitting stations transmits a broadcasting signal to the up transmission line via the one of the plurality of communication channels assigned to the each transmitting station, which corresponds to a desired broadcasting area.
- a signal transmitted to the broadcasting satellite via the up transmission line is received by the reception antenna and separated by the channel separating means into signals corresponding to communication channels that are set on the up transmission line.
- Those of the thus-separated signals corresponding to the communication channels, which correspond to predetermined communication channels, are multiplexed and amplified by signal processing means that correspond to a plurality of radiators incorporated in the transmitting antenna, and are then output to the radiators corresponding to the signal processing means.
- the radiators emit the signals to areas defined by the transmission beams of the radiators.
- a broadcasting signal transmitted from each transmitting station is transmitted from a radiator corresponding to a communication channel which was used to transmit the broadcasting signal, to an area defined by the transmission beam of the radiator.
- the transmitting station can determine a broadcasting area by selecting a communication channel to be used to transmit a broadcasting signal.
- the plurality of communication channels include communication channels that correspond to the respective radiators, and a communication channel corresponding to a plurality of ones of the radiators.
- corresponding signal processing means multiplexes the signals.
- the broadcasting area is not limited to the area defined by the transmission beam of each radiator, but an area that is obtained by combining areas defined by the transmission beams of a plurality of radiators can be used as one broadcasting area unit, thereby enhancing the flexibility of use of the communication system.
- each of the transmitting stations constructed as above transmits a broadcasting signal obtained by spread spectrum modulation. Further, when a plurality of signals are transmitted to each radiator through corresponding communication channels, the signal processing means multiplexes the signals by synthesizing them.
- FIG. 1 is a schematic view illustrating a satellite broadcasting system according to the embodiment of the invention.
- the satellite broadcasting system includes a plurality of (two in this case) broadcasting stations BC1 and BC2 and a broadcasting satellite SAT.
- the broadcasting stations BC1 and BC2 transmit program signals created and edited by, for example, broadcasting enterprisers, to the broadcasting satellite SAT via an up transmission line of a Ka band.
- the broadcasting satellite SAT is managed by a satellite tracking control station STCC so that, for example, it will remain stationary at a predetermined location of a stationary orbit above the equator.
- the broadcasting satellite SAT is constructed, for example, as shown in FIG. 2.
- reference numeral 1 denotes a satellite main body.
- the satellite main body 1 has solar battery panels 2 and 3, a Ka-band antenna 4, and an S-band antenna 5 attached thereto.
- the Ka-band antenna 4 is formed of a reflection mirror 41 having a diameter of, for example, 2.5 m, and a primary radiator 42.
- the S-band antenna 5 is formed of a reflection mirror 51 having a diameter of, for example, 15 m, and a primary radiator group 52.
- a broadcasting signal transmitted from each of the broadcasting stations BC1 and BC2 is received by the Ka-band antenna 4, then demodulated and amplified by a signal processing device (which will be described later) installed in the satellite main body 1, and converted into an S-band signal.
- the thus-converted broadcasting signal is transmitted from the S-band antenna 5 to a service area via an S-band down transmission line.
- a broadcasting signal from the broadcasting satellite SAT is received by a fixed station installed in an office or a home, or by a mobile station MS such as a receiving device installed in a car, a portable terminal device, etc.
- a plurality of (about 900 at maximum) channels of a transmission rate of, for example, 64 - 256 kbps/channel are multiplexed.
- a MPEG 4 Moving Picture Expert Group 4
- an image encoding system is used as an image encoding system.
- the primary radiator group 52 of the S-band antenna 5 has a plurality of (four in this embodiment) primary radiators for transmitting respective beams to divided portions (four portions in this embodiment) of the service area.
- FIG. 3 shows an example of a beam arrangement assumed when the service area is divided into four portions.
- reference numerals #1 - #4 denote signal receiving areas defined by different transmission beams.
- FIG. 4 is a block diagram illustrating the structure of a signal processing device installed in the satellite main body 1.
- reference numeral 10 denotes the signal processing device, which comprises a low noise amplifier 11, five band-pass filters 12 (12-1 - 12-5), five mixers 13 (13-1 - 13-5), five oscillators 14 (14-1 - 14-5), four synthesizers 15 (15-1 - 15-4) and four high-output amplifiers 16 (16-1 - 16-4).
- a broadcasting signal received by the Ka-band antenna 4 is supplied to the low noise amplifier 11, where it is amplified.
- the amplified signal is supplied to each of the band-pass filters 12-1 - 12-5.
- the band-pass filter 12-1 passes therethrough a signal component with a band width of a predetermined central frequency f1 and ⁇ B.
- the signal having passed through the band-pass filter 12-1 is mixed, by the mixer 13-1, with a signal with a frequency of (f1 - fs) generated by the oscillator 14-1, thereby being converted into a signal with a central frequency of fs. This signal is supplied to the synthesizer 15-1.
- a combination of the band-pass filter 12-2, the mixer 13-2 and the oscillator 14-2, a combination of the band-pass filter 12-3, the mixer 13-3 and the oscillator 14-3, and a combination of the band-pass filter 12-4, the mixer 13-4 and the oscillator 14-4 perform the same processing as in the combination of the band-pass filter 12-1, the mixer 13-1 and the oscillator 14-1, thereby converting a signal output from the low noise amplifier 11 into signals of the central frequency fs and then supplying the signals to the synthesizers 15-2 - 15-4, respectively.
- a signal output from the low noise amplifier 11 is converted, as in the combination of the band-pass filter 12-1, the mixer 13-1 and the oscillator 14-1, into a signal of the central frequency fs, which is then supplied to all the synthesizers 15-1 - 15-4.
- the band-pass filters 12-2 - 12-5 each pass therethrough a signal component with a band width of a corresponding central frequency f2 - f5 and ⁇ B, which differs from the case of the band-pass filter 12-1.
- the oscillators 14-2 - 14-5 each generate a signal with a frequency that is equal to the difference between the central frequency of a corresponding band-pass filter 12-2 - 12-5 and the frequency fs.
- the synthesizers 15-1 - 15-4 each synthesize a signal output from a corresponding one of the mixers 13-1 - 13-4, with a signal output from the mixer 13-5.
- a synthesized signal output from each of the synthesizers 15-1 - 15-4 is amplified by a corresponding one of the high power amplifiers 16-1 - 16-4, and then supplied to corresponding one of four primary radiators 53-1 - 53-4 that constitute the primary radiator group 52 of the S-band antenna 5.
- first to fifth communication channels having respective central frequencies f1 - f5 are set on the up transmission line by frequency division.
- the first to fourth communication channels of the five communication channels correspond to the signal receiving areas #1 - #4, respectively, and are set to serve as communication channels for transmitting broadcasting signals that limit respective broadcasting ranges of the areas #1 - #4.
- the fifth communication channel is set to serve as a communication channel for transmitting a broadcasting signal that sets all the signal receiving areas #1 - #4 (the entire service area) as a broadcasting range.
- the satellite broadcasting system of the embodiment does not have a feeder link station for receiving a broadcasting signal from each broadcasting station BC1 or BC2, and transmitting it to the broadcasting satellite SAT. Instead, the broadcasting stations BC1 and BC2 individually transmit broadcasting signals to the up transmission line. Further, a communication channel used for the transmission of a broadcasting signal must correspond to the broadcasting range for which the broadcasting signal is to be transmitted. Moreover, a broadcasting signal to be transmitted by each broadcasting station BC1 or BC2 must be a signal obtained by spread spectrum modulation performed, at the signal receiving terminal side, using a diffusion sign that corresponds to a selection number (so-called a channel number) for the selection of the broadcasting signal.
- broadcasting signals transmitted from the broadcasting stations BC1 and BC2 are received by the Ka-band antenna 4.
- the Ka-band antenna 4 actually receives a signal obtained by synthesizing the broadcasting signals from the broadcasting stations BC1 and BC2.
- the signal received by the Ka-band antenna 4 is amplified by the low noise amplifier 11, then guided to the band-pass filters 12-1 - 12-5, where the signal is divided into broadcasting signals of respective communication channels (a plurality of broadcasting signals having different diffusion signs used for the spread spectrum modification).
- the broadcasting signals divided by the band-pass filters 12-1 - 12-5 are guided to the mixers 13 and the oscillators 14, where they are subjected to frequency conversion so that their respective central frequencies are unified to fs.
- the broadcasting signals obtained, after the frequency conversion, through the first to fourth communication channels are synthesized by the respective synthesizers 15 with a signal transmitted through the fifth communication channel.
- the broadcasting signal obtained by synthesizing the broadcasting signal transmitted through the first communication channel, with the broadcasting signal transmitted through the fifth communication channel is supplied to the primary radiator 53-1 after it is amplified by the high power amplifier 16-1, and is transmitted to the signal receiving area #1 by the S-band antenna 5.
- the broadcasting signal obtained by synthesizing the broadcasting signal transmitted through the second communication channel, with the broadcasting signal transmitted through the fifth communication channel is supplied to the primary radiator 53-2 after it is amplified by the high power amplifier 16-2, and is transmitted to the signal receiving area #2 by the S-band antenna 5.
- the broadcasting signal obtained by synthesizing the broadcasting signal transmitted through the third communication channel, with the broadcasting signal transmitted through the fifth communication channel is supplied to the primary radiator 53-3 after it is amplified by the high power amplifier 16-3, and is transmitted to the signal receiving area #3 by the S-band antenna 5.
- the broadcasting signal obtained by synthesizing the broadcasting signal transmitted through the fourth communication channel, with the broadcasting signal transmitted through the fifth communication channel is supplied to the primary radiator 53-4 after it is amplified by the high power amplifier 16-4, and is transmitted to the signal receiving area #4 by the S-band antenna 5.
- each broadcasting signal s1 - s5 is transmitted to the broadcasting satellite SAT through a corresponding one of the first to fifth communication channels
- a broadcasting signal obtained by synthesizing the broadcasting signals s1 and s5 in the same frequency band (having the central frequency of fs) is transmitted from the primary radiator 53-1 to the signal receiving area #1.
- a broadcasting signal obtained by synthesizing the broadcasting signals s2 and s5 in the seine frequency band (having the central frequency of fs) is transmitted from the primary radiator 53-2 to the signal receiving area #2.
- a broadcasting signal obtained by synthesizing the broadcasting signals s3 and s5 in the same frequency band (having the central frequency of fs) is transmitted from the primary radiator 53-3 to the signal receiving area #3.
- a broadcasting signal obtained by synthesizing the broadcasting signals s4 and s5 in the same frequency band (having the central frequency of fs) is transmitted from the primary radiator 53-4 to the signal receiving area #4.
- broadcasting signals corresponding to the broadcasting signals s11 and s12 but having a frequency band with the central frequency of fs are transmitted from the primary radiator 53-1 of the broadcasting satellite SAT to the signal receiving area #1, whereas no signal is transmitted from the other primary radiators 53-2 - 53-4 to the areas #2 - #4.
- a broad-casting signal corresponding to the broadcasting signal s5 but having a frequency band with the central frequency of fs is transmitted from the primary radiators 53-1 - 53-4 of the broadcasting satellite SAT to the signal receiving areas #1 - #4.
- any broadcasting signal transmitted through the fifth communication channel from each of the broadcasting stations BC1 and BC2 is transmitted to all the signal receiving areas #1 - #4. Accordingly, each broadcasting station BC1 or BC2 can use all the signal receiving areas #1 - #4 (i.e. the entire service area) as the broadcasting range by using the fifth communication channel.
- a broadcasting signal transmitted through each of the first to fourth communication channels from each of the broadcasting stations BC1 and BC2 is transmitted only to a corresponding one of the signal receiving areas #1 - #4. Accordingly, each broadcasting station BC1 or BC2 can use each of the signal receiving areas #1 - #4 as the broadcasting range by using a corresponding one of the first to fourth communication channels.
- each broadcasting station BC1 or BC2 can control the area to which a broadcasting signal is transmitted from the broadcasting satellite SAT, flexible use can be expected. Further, since neither a feeder link station nor a ground communication device is required, the system structure can be simplified.
- each broadcasting signal is subjected, at the signal receiving terminal side, to spread spectrum modification using a diffusion sign that corresponds to a selection number (so-called a channel number) for the selection of the broadcasting signal. Therefore, even if different broadcasting signals directed to the same broadcasting range are simultaneously transmitted from one or both of the broadcasting stations BC1 and BC2, they are prevented from interfering with each other and can be received correctly by a signal receiving terminal. Moreover, even when the broadcasting satellite SAT has a plurality of broadcasting signals to be transmitted to one signal receiving area, the processing of each synthesizer 15 is relatively simple since the broadcasting signals are spread-spectrum modified and hence prevented from interfering with each other. As a result, the synthesizers 15 can have a simple structure.
- each of the broadcasting stations BC1 and BC2 may have a function for collecting broadcasting signals transmitted from, for example, other broadcasting stations that have no satellite communication equipments, and transmitting them.
- the communication channels set on the up transmission line are made to correspond to the signal receiving areas #1 - #4, respectively, or to all of the signal receiving areas #1 - #4, any other correspondence may be optionally employed. For example, if a communication channel corresponding to both the signal receiving areas #1 and #2, and a communication channel corresponding to both the signal receiving areas #3 and #4 are set, broadcasting ranges such as "East Japan” and "West Japan” can be selected.
- each signal receiving area is not limited to that shown in FIG. 3, but may be modified optionally.
- the communication channels on the up transmission line are set by frequency division, they may be set by time division or any other multiplex method.
- the down transmission line transmits a multiplex signal obtained by CDM (Code Division Multiplex), another multiplex method such as OFDM (Orthogonal Frequency Division Multiplex), TDM (Time Division Multiplex), etc. may be used to create the multiplex signal.
- CDM Code Division Multiplex
- OFDM Orthogonal Frequency Division Multiplex
- TDM Time Division Multiplex
- a signal transmitted by a broadcasting station through the up transmission line is not limited to the signal obtained by spread spectrum modification.
- the present invention provides a satellite broadcasting system that uses a broadcasting satellite located in a stationary orbit above the equator to provide a user with broadcasting signals transmitted from a plurality of transmitting stations, characterized in that the broadcasting satellite comprises: a reception antenna for receiving a signal transmitted via an up transmission line that includes a plurality of communication channels; a transmission antenna having a plurality of radiators for emitting transmission beams to a plurality of areas; channel separating means for extracting, from signals received by the reception antenna, a signal transmitted through each of the plurality of communication channels; and a plurality of signal processing means provided corresponding to the plurality of radiators for taking those signals included in signals transmitted through the communication channels and extracted by the channel separating means, which correspond to communication channels assigned in advance to the plurality of signal processing means, thereby amplifying and outputting the taken signals to the plurality of radiators, and characterized in that each of the plurality of transmitting stations transmits a broadcasting signal to the up transmission line via the one of the plurality of communication
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Abstract
In a broadcasting satellite, signals transmitted
through an up transmission line of a Ka band, which
includes a plurality of communication channels, are
received by a Ka-band antenna. The signals received by
the antenna are passed through band-pass filters 12 to
thereby extract a broadcasting signal transmitted
through each communication channel. Those of the thus-extracted
broadcasting signals, which have been
transmitted through predetermined communication
channels, are synthesized by each of synthesizers 15,
then amplified by a corresponding one of high power
amplifiers 16, and output to a corresponding one of a
plurality of primary radiators 53 employed in an S-band
antenna. The S-band antenna transmits each synthesized
signal to a predetermined area that corresponds to a
corresponding primary radiator 53. Thus, the system
can be made to a simple structure, and the service area
can be changed for each broadcasting signal.
Description
This invention relates to a satellite broadcasting
system for providing broadcasting of images, voices,
data, etc., using a broadcasting satellite located in a
stationary orbit above the equator, and also to the
broadcasting satellite used for the satellite
broadcasting.
In accordance with the demand for various kinds of
broadcasting services and with the development of
communication techniques, satellite broadcasting has
been started in addition to ground broadcasting. Since
satellite broadcasting can provide services in a wide
area without establishing a large-scale infrastructure,
attention is now paid to it as a medium that can
satisfy many needs.
At present in Japan, BS (Broadcasting Satellite)
broadcasting and CS (Communication Satellite)
broadcasting are now put to practical use, and the use
of digital broadcasting has been started. Also in
foreign countries, a satellite broadcasting system of
substantially the same scale as in Japan has been
developed and put to practical use.
In the satellite broadcasting systems used in both
Japan and foreign countries, certain transmitting
stations collect broadcasting signals of a plurality of
channels and multiplex them before transmitting them to
an up transmission line leading to the broadcasting
satellite. The broadcasting satellite, in turn,
converts the frequency of each signal input thereto via
the up transmission line, to a value corresponding to a
down transmission line to the ground, and performs
power amplification of each signal, thereby
transmitting each resultant signal to a predetermined
service area. Thus, all broadcasting signals of a
plurality of channels are transmitted to the
predetermined service area. In other words,
broadcasting is always performed only for a single
service area.
Furthermore, a feeder link station is necessary
for collecting broadcasting signals of a plurality of
channels, and then transmitting them to the up
transmission line. In the case of collecting
broadcasting signals from a broadcasting station in a
real-time manner, it is necessary to secure a ground
transmission line between the broadcasting station and
the feeder link station, which inevitably makes the
system complicated.
As stated above, in the conventional satellite
broadcasting system, a particular feeder link station
concentrically performs signal transmission to a
broadcasting satellite, and the broadcasting satellite
itself only relays signals transmitted from the feeder
link station. Accordingly, the system structure is
complicated, and the service area is disadvantageously
inflexible.
The present invention has been developed in
light of the above, and is aimed at providing a
satellite communication system of a simple structure
capable of changing the service area for each of
broadcasting signals, and also providing a broadcasting
satellite that enables the satellite communication
system.
To attain the aim, the invention provides a
satellite broadcasting system that uses a broadcasting
satellite located in a stationary orbit above the
equator to provide a user with broadcasting from a
plurality of transmitting stations such as broadcasting
stations, characterized in that the broadcasting
satellite comprises: a reception antenna such as a
Ka-band antenna for receiving a signal transmitted
via a predetermined up transmission line on which a
plurality of communication channels are set; a
transmission antenna such as an S-band antenna having a
plurality of radiators for emitting transmission beams
to a plurality of areas; channel separating means such
as a band-pass filter for extracting, from the signal
received by the reception antenna, a signal transmitted
through each of the plurality of communication
channels; and a plurality of signal processing means
such as synthesizers, high power amplifiers, etc.
provided corresponding to the plurality of radiators
for each multiplexing and amplifying predetermined
signals included in signals transmitted through the
communication channels and extracted by the channel
separating means, thereby outputting each signal to a
corresponding one of the radiators, and characterized
in that each of the plurality of transmitting stations
transmits a broadcasting signal to the up transmission
line via the one of the plurality of communication
channels assigned to the each transmitting station,
which corresponds to a desired broadcasting area.
By employing the above-described means, a signal
transmitted to the broadcasting satellite via the up
transmission line is received by the reception antenna
and separated by the channel separating means into
signals corresponding to communication channels that
are set on the up transmission line. Those of the
thus-separated signals corresponding to the communication
channels, which correspond to predetermined
communication channels, are multiplexed and amplified
by signal processing means that correspond to a
plurality of radiators incorporated in the transmitting
antenna, and are then output to the radiators
corresponding to the signal processing means. The
radiators, in turn, emit the signals to areas defined
by the transmission beams of the radiators. Accordingly,
a broadcasting signal transmitted from each
transmitting station is transmitted from a radiator
corresponding to a communication channel which was used
to transmit the broadcasting signal, to an area defined
by the transmission beam of the radiator. In other
words, the transmitting station can determine a
broadcasting area by selecting a communication channel
to be used to transmit a broadcasting signal.
Further, in the invention, the plurality of
communication channels include communication channels
that correspond to the respective radiators, and a
communication channel corresponding to a plurality of
ones of the radiators. When there exist a plurality of
signals transmitted through a plurality of communication
channels and corresponding to radiators,
corresponding signal processing means multiplexes the
signals.
By employing the above means, a signal transmitted
to the broadcasting satellite through a communication
channel that corresponds to a plurality of ones of the
radiators is transmitted to a plurality of areas from
the radiators corresponding to the communication
channel. Thus, the broadcasting area is not limited to
the area defined by the transmission beam of each
radiator, but an area that is obtained by combining
areas defined by the transmission beams of a plurality
of radiators can be used as one broadcasting area unit,
thereby enhancing the flexibility of use of the
communication system.
In addition, in the invention, each of the
transmitting stations constructed as above transmits a
broadcasting signal obtained by spread spectrum
modulation. Further, when a plurality of signals are
transmitted to each radiator through corresponding
communication channels, the signal processing means
multiplexes the signals by synthesizing them.
Since signals obtained by spread spectrum
modulation do not interfere with each other,
synthesization performed by the signal processing means
is relatively simple processing. That the signal
processing means performs simple processing implies
that the system structure can be simplified.
The embodiment of the invention will be described
with reference to the accompanying drawings.
FIG. 1 is a schematic view illustrating a
satellite broadcasting system according to the
embodiment of the invention. The satellite
broadcasting system includes a plurality of (two in
this case) broadcasting stations BC1 and BC2 and a
broadcasting satellite SAT. The broadcasting stations
BC1 and BC2 transmit program signals created and edited
by, for example, broadcasting enterprisers, to the
broadcasting satellite SAT via an up transmission line
of a Ka band. The broadcasting satellite SAT is
managed by a satellite tracking control station STCC so
that, for example, it will remain stationary at a
predetermined location of a stationary orbit above the
equator.
The broadcasting satellite SAT is constructed, for
example, as shown in FIG. 2. In FIG. 2, reference
numeral 1 denotes a satellite main body. The satellite
main body 1 has solar battery panels 2 and 3, a Ka-band
antenna 4, and an S-band antenna 5 attached thereto.
The Ka-band antenna 4 is formed of a reflection mirror
41 having a diameter of, for example, 2.5 m, and a
primary radiator 42. The S-band antenna 5 is formed of
a reflection mirror 51 having a diameter of, for
example, 15 m, and a primary radiator group 52.
A broadcasting signal transmitted from each of the
broadcasting stations BC1 and BC2 is received by the
Ka-band antenna 4, then demodulated and amplified by a
signal processing device (which will be described
later) installed in the satellite main body 1, and
converted into an S-band signal. The thus-converted
broadcasting signal is transmitted from the S-band
antenna 5 to a service area via an S-band down
transmission line.
As is shown in FIG. 1, in the service area, a
broadcasting signal from the broadcasting satellite SAT
is received by a fixed station installed in an office
or a home, or by a mobile station MS such as a
receiving device installed in a car, a portable
terminal device, etc.
In the S-band down transmission line, a plurality
of (about 900 at maximum) channels of a transmission
rate of, for example, 64 - 256 kbps/channel are
multiplexed. Further, when transmitting an image
signal via each channel, a MPEG 4 (Moving Picture
Expert Group 4), for example, is used as an image
encoding system.
The primary radiator group 52 of the S-band
antenna 5 has a plurality of (four in this embodiment)
primary radiators for transmitting respective beams to
divided portions (four portions in this embodiment) of
the service area. FIG. 3 shows an example of a beam
arrangement assumed when the service area is divided
into four portions. In FIG. 3, reference numerals
#1 - #4 denote signal receiving areas defined by
different transmission beams.
FIG. 4 is a block diagram illustrating the
structure of a signal processing device installed in
the satellite main body 1. In FIG. 4, reference
numeral 10 denotes the signal processing device, which
comprises a low noise amplifier 11, five band-pass
filters 12 (12-1 - 12-5), five mixers 13 (13-1 - 13-5),
five oscillators 14 (14-1 - 14-5), four synthesizers
15 (15-1 - 15-4) and four high-output amplifiers 16
(16-1 - 16-4).
A broadcasting signal received by the Ka-band
antenna 4 is supplied to the low noise amplifier 11,
where it is amplified. The amplified signal is
supplied to each of the band-pass filters 12-1 - 12-5.
The band-pass filter 12-1 passes therethrough a
signal component with a band width of a predetermined
central frequency f1 and ±B. The signal having passed
through the band-pass filter 12-1 is mixed, by the
mixer 13-1, with a signal with a frequency of (f1 - fs)
generated by the oscillator 14-1, thereby being
converted into a signal with a central frequency of fs.
This signal is supplied to the synthesizer 15-1.
A combination of the band-pass filter 12-2, the
mixer 13-2 and the oscillator 14-2, a combination of
the band-pass filter 12-3, the mixer 13-3 and the
oscillator 14-3, and a combination of the band-pass
filter 12-4, the mixer 13-4 and the oscillator 14-4
perform the same processing as in the combination of
the band-pass filter 12-1, the mixer 13-1 and the
oscillator 14-1, thereby converting a signal output
from the low noise amplifier 11 into signals of the
central frequency fs and then supplying the signals to
the synthesizers 15-2 - 15-4, respectively. Similarly,
in a combination of the band-pass filter 12-5, the
mixer 13-5 and the oscillator 14-5, a signal output
from the low noise amplifier 11 is converted, as in the
combination of the band-pass filter 12-1, the mixer
13-1 and the oscillator 14-1, into a signal of the
central frequency fs, which is then supplied to all the
synthesizers 15-1 - 15-4.
However, it should be noted that the band-pass
filters 12-2 - 12-5 each pass therethrough a signal
component with a band width of a corresponding central
frequency f2 - f5 and ±B, which differs from the case
of the band-pass filter 12-1. Further, the oscillators
14-2 - 14-5 each generate a signal with a frequency
that is equal to the difference between the central
frequency of a corresponding band-pass filter 12-2 -
12-5 and the frequency fs.
The synthesizers 15-1 - 15-4 each synthesize a
signal output from a corresponding one of the mixers
13-1 - 13-4, with a signal output from the mixer 13-5.
A synthesized signal output from each of the
synthesizers 15-1 - 15-4 is amplified by a
corresponding one of the high power amplifiers 16-1 -
16-4, and then supplied to corresponding one of four
primary radiators 53-1 - 53-4 that constitute the
primary radiator group 52 of the S-band antenna 5.
The operation of the satellite broadcasting system
constructed as above will be described.
Suppose that the four primary radiators 53-1 -
53-4 that constitute the primary radiator group 52 of
the S-band antenna 5 provide transmission beams for the
signal receiving areas #1 - #4 shown in FIG. 3. Also
suppose that communication channels (hereinafter
referred to as "first to fifth communication channels")
having respective central frequencies f1 - f5 are set
on the up transmission line by frequency division. The
first to fourth communication channels of the five
communication channels correspond to the signal
receiving areas #1 - #4, respectively, and are set to
serve as communication channels for transmitting
broadcasting signals that limit respective broadcasting
ranges of the areas #1 - #4. The fifth communication
channel is set to serve as a communication channel for
transmitting a broadcasting signal that sets all the
signal receiving areas #1 - #4 (the entire service
area) as a broadcasting range.
The satellite broadcasting system of the
embodiment does not have a feeder link station for
receiving a broadcasting signal from each broadcasting
station BC1 or BC2, and transmitting it to the
broadcasting satellite SAT. Instead, the broadcasting
stations BC1 and BC2 individually transmit broadcasting
signals to the up transmission line. Further, a
communication channel used for the transmission of a
broadcasting signal must correspond to the broadcasting
range for which the broadcasting signal is to be
transmitted. Moreover, a broadcasting signal to be
transmitted by each broadcasting station BC1 or BC2
must be a signal obtained by spread spectrum modulation
performed, at the signal receiving terminal side, using
a diffusion sign that corresponds to a selection number
(so-called a channel number) for the selection of the
broadcasting signal.
Thus, broadcasting signals transmitted from the
broadcasting stations BC1 and BC2 are received by the
Ka-band antenna 4. The Ka-band antenna 4 actually
receives a signal obtained by synthesizing the
broadcasting signals from the broadcasting stations BC1
and BC2.
The signal received by the Ka-band antenna 4 is
amplified by the low noise amplifier 11, then guided to
the band-pass filters 12-1 - 12-5, where the signal is
divided into broadcasting signals of respective
communication channels (a plurality of broadcasting
signals having different diffusion signs used for the
spread spectrum modification). The broadcasting
signals divided by the band-pass filters 12-1 - 12-5
are guided to the mixers 13 and the oscillators 14,
where they are subjected to frequency conversion so
that their respective central frequencies are unified
to fs.
Subsequently, the broadcasting signals obtained,
after the frequency conversion, through the first to
fourth communication channels are synthesized by the
respective synthesizers 15 with a signal transmitted
through the fifth communication channel.
The broadcasting signal obtained by synthesizing
the broadcasting signal transmitted through the first
communication channel, with the broadcasting signal
transmitted through the fifth communication channel is
supplied to the primary radiator 53-1 after it is
amplified by the high power amplifier 16-1, and is
transmitted to the signal receiving area #1 by the
S-band antenna 5. The broadcasting signal obtained by
synthesizing the broadcasting signal transmitted
through the second communication channel, with the
broadcasting signal transmitted through the fifth
communication channel is supplied to the primary
radiator 53-2 after it is amplified by the high power
amplifier 16-2, and is transmitted to the signal
receiving area # 2 by the S-band antenna 5. The
broadcasting signal obtained by synthesizing the
broadcasting signal transmitted through the third
communication channel, with the broadcasting signal
transmitted through the fifth communication channel is
supplied to the primary radiator 53-3 after it is
amplified by the high power amplifier 16-3, and is
transmitted to the signal receiving area # 3 by the
S-band antenna 5. The broadcasting signal obtained by
synthesizing the broadcasting signal transmitted
through the fourth communication channel, with the
broadcasting signal transmitted through the fifth
communication channel is supplied to the primary
radiator 53-4 after it is amplified by the high power
amplifier 16-4, and is transmitted to the signal
receiving area # 4 by the S-band antenna 5.
Thus, where as shown in FIG. 5, each broadcasting
signal s1 - s5 is transmitted to the broadcasting
satellite SAT through a corresponding one of the first
to fifth communication channels, a broadcasting signal
obtained by synthesizing the broadcasting signals s1
and s5 in the same frequency band (having the central
frequency of fs) is transmitted from the primary
radiator 53-1 to the signal receiving area #1.
Similarly, a broadcasting signal obtained by
synthesizing the broadcasting signals s2 and s5 in the
seine frequency band (having the central frequency of
fs) is transmitted from the primary radiator 53-2 to
the signal receiving area # 2. Further, a broadcasting
signal obtained by synthesizing the broadcasting
signals s3 and s5 in the same frequency band (having
the central frequency of fs) is transmitted from the
primary radiator 53-3 to the signal receiving area # 3.
A broadcasting signal obtained by synthesizing the
broadcasting signals s4 and s5 in the same frequency
band (having the central frequency of fs) is
transmitted from the primary radiator 53-4 to the
signal receiving area # 4.
On the other hand, where as shown in FIG. 6, only
one broadcasting signal s1 is transmitted only through
the first communication channel to the broadcasting
satellite SAT, a broadcasting signal corresponding to
the broadcasting signal s1 but having a frequency band
with the central frequency of fs is transmitted from
the primary radiator 53-1 of the broadcasting satellite
SAT to the signal receiving area #1, whereas no signal
is transmitted from the other primary radiators 53-2 -
53-4 to the areas #2 - #4.
In addition, where as shown in FIG. 7, only two
broadcasting signals s11 and s12 is transmitted only
through the first communication channel to the
broadcasting satellite SAT, broadcasting signals
corresponding to the broadcasting signals s11 and s12
but having a frequency band with the central frequency
of fs are transmitted from the primary radiator 53-1 of
the broadcasting satellite SAT to the signal receiving
area #1, whereas no signal is transmitted from the
other primary radiators 53-2 - 53-4 to the areas
#2 - #4.
Furthermore, where only one broadcasting signal s5
is transmitted only through the fifth communication
channel to the broadcasting satellite SAT, a broad-casting
signal corresponding to the broadcasting signal
s5 but having a frequency band with the central
frequency of fs is transmitted from the primary
radiators 53-1 - 53-4 of the broadcasting satellite SAT
to the signal receiving areas #1 - #4.
As described above, in the embodiment, any
broadcasting signal transmitted through the fifth
communication channel from each of the broadcasting
stations BC1 and BC2 is transmitted to all the signal
receiving areas #1 - #4. Accordingly, each broadcasting
station BC1 or BC2 can use all the signal
receiving areas #1 - #4 (i.e. the entire service area)
as the broadcasting range by using the fifth communication
channel.
Also, a broadcasting signal transmitted through
each of the first to fourth communication channels from
each of the broadcasting stations BC1 and BC2 is
transmitted only to a corresponding one of the signal
receiving areas #1 - #4. Accordingly, each
broadcasting station BC1 or BC2 can use each of the
signal receiving areas #1 - #4 as the broadcasting
range by using a corresponding one of the first to
fourth communication channels.
Since each broadcasting station BC1 or BC2 can
control the area to which a broadcasting signal is
transmitted from the broadcasting satellite SAT,
flexible use can be expected. Further, since neither a
feeder link station nor a ground communication device
is required, the system structure can be simplified.
As described above, each broadcasting signal is
subjected, at the signal receiving terminal side, to
spread spectrum modification using a diffusion sign
that corresponds to a selection number (so-called a
channel number) for the selection of the broadcasting
signal. Therefore, even if different broadcasting
signals directed to the same broadcasting range are
simultaneously transmitted from one or both of the
broadcasting stations BC1 and BC2, they are prevented
from interfering with each other and can be received
correctly by a signal receiving terminal. Moreover,
even when the broadcasting satellite SAT has a
plurality of broadcasting signals to be transmitted to
one signal receiving area, the processing of each
synthesizer 15 is relatively simple since the
broadcasting signals are spread-spectrum modified and
hence prevented from interfering with each other. As a
result, the synthesizers 15 can have a simple structure.
The present invention is not limited to the abovedescribed
embodiment. Although, for example, no feeder
link station is employed in the embodiment, each of the
broadcasting stations BC1 and BC2 may have a function
for collecting broadcasting signals transmitted from,
for example, other broadcasting stations that have no
satellite communication equipments, and transmitting
them.
Yet further, although in the embodiment, the
communication channels set on the up transmission line
are made to correspond to the signal receiving areas
#1 - #4, respectively, or to all of the signal
receiving areas #1 - #4, any other correspondence
may be optionally employed. For example, if a
communication channel corresponding to both the signal
receiving areas #1 and #2, and a communication channel
corresponding to both the signal receiving areas # 3 and
#4 are set, broadcasting ranges such as "East Japan"
and "West Japan" can be selected.
Although in the embodiment, two broadcasting
stations are provided and the service area is divided
into four signal receiving areas, the number of
broadcasting stations or the number of signal receiving
areas is optional. The shape of each signal receiving
area is not limited to that shown in FIG. 3, but may be
modified optionally.
Although in the embodiment, the communication
channels on the up transmission line are set by
frequency division, they may be set by time division or
any other multiplex method.
Furthermore, although in the embodiment, the down
transmission line transmits a multiplex signal obtained
by CDM (Code Division Multiplex), another multiplex
method such as OFDM (Orthogonal Frequency Division
Multiplex), TDM (Time Division Multiplex), etc. may be
used to create the multiplex signal. When changing the
multiplex method used on the down transmission line, it
is desirable that the format of a signal transmitted
through the up transmission line should be made to
correspond to the multiplex method employed on the
down transmission line. In other words, a signal
transmitted by a broadcasting station through the up
transmission line is not limited to the signal obtained
by spread spectrum modification.
The present invention can be modified in various
manners without departing from its scope.
As described above, the present invention provides
a satellite broadcasting system that uses a broadcasting
satellite located in a stationary orbit above
the equator to provide a user with broadcasting signals
transmitted from a plurality of transmitting stations,
characterized in that the broadcasting satellite
comprises: a reception antenna for receiving a signal
transmitted via an up transmission line that includes a
plurality of communication channels; a transmission
antenna having a plurality of radiators for emitting
transmission beams to a plurality of areas; channel
separating means for extracting, from signals received
by the reception antenna, a signal transmitted through
each of the plurality of communication channels; and
a plurality of signal processing means provided
corresponding to the plurality of radiators for taking
those signals included in signals transmitted through
the communication channels and extracted by the channel
separating means, which correspond to communication
channels assigned in advance to the plurality of signal
processing means, thereby amplifying and outputting the
taken signals to the plurality of radiators, and
characterized in that each of the plurality of
transmitting stations transmits a broadcasting signal
to the up transmission line via the one of the
plurality of communication channels assigned to said
each transmitting station, which corresponds to a
desired broadcasting area. By virtue of this design,
the system can be made to a simple structure, and the
service area can be changed for each broadcasting
signal.
Claims (6)
- A satellite broadcasting system that uses a broadcasting satellite located in a stationary orbit above the equator to provide a user with broadcasting signals transmitted from a plurality of transmitting stations, characterized in thatthe broadcasting satellite comprises:a reception antenna for receiving a signal transmitted via an up transmission line that includes a plurality of communication channels;a transmission antenna having a plurality of radiators for emitting transmission beams to a plurality of areas;channel separating means for extracting, from the signal received by the reception antenna, a signal transmitted through each of the plurality of communication channels; anda plurality of signal processing means provided corresponding to the plurality of radiators for taking those signals included in signals transmitted through the communication channels and extracted by the channel separating means, which correspond to communication channels assigned in advance to the plurality of signal processing means, thereby amplifying and outputting the taken signals to the plurality of radiators,and characterized in thateach of the plurality of transmitting stations transmits a broadcasting signal to the up transmission line via the one of the plurality of communication channels assigned to said each transmitting station, which corresponds to a desired broadcasting area.
- A satellite broadcasting system according to claim 1, characterized in that each of the plurality of signal processing means multiplexes signals transmitted through those of the plurality of communication channels which are in advance assigned thereto, thereby outputting a multiplexing result to a corresponding one of the radiators.
- A satellite broadcasting system according to claim 1 or 2, characterized in that each of the plurality of transmitting stations transmits a broadcasting signal obtained by spread spectrum modulation, and that each of the plurality of signal processing means synthesizes, when a plurality of communication channels are assigned thereto in advance, signals transmitted through the communication channels, thereby performing multiplexing.
- A broadcasting satellite characterized by comprising:a reception antenna for receiving a signal transmitted via an up transmission line that includes a plurality of communication channels;a transmission antenna having a plurality of radiators for emitting transmission beams to a plurality of areas;channel separating means for extracting, from the signal received by the reception antenna, a signal transmitted through each of the plurality of communication channels; anda plurality of signal processing means provided corresponding to the plurality of radiators for taking those signals included in signals transmitted through the communication channels and extracted by the channel separating means, which correspond to communication channels assigned in advance to the plurality of signal processing means, thereby amplifying and outputting the taken signals to the plurality of radiators.
- A broadcasting satellite according to claim 4, characterized in that each of the plurality of signal processing means multiplexes signals transmitted through those of the plurality of communication channels which are in advance assigned thereto, thereby outputting a multiplexing result to a corresponding one of the radiators.
- A broadcasting satellite according to claim 4 or 5, characterized in that each of the plurality of signal processing means synthesizes signals transmitted through the communication channels, thereby performing multiplexing, when the signals transmitted through the communication channels are obtained by spread spectrum modulation, and when a plurality of ones of the communication channels are assigned in advance to said each of the signal processing means.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9141901A JPH10336145A (en) | 1997-05-30 | 1997-05-30 | Satellite broadcast system and broadcast satellite |
JP14190197 | 1997-05-30 | ||
PCT/JP1998/002391 WO1998054852A1 (en) | 1997-05-30 | 1998-05-29 | Satellite broadcasting system and broadcasting satellite |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0984569A1 true EP0984569A1 (en) | 2000-03-08 |
Family
ID=15302803
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98921890A Withdrawn EP0984569A1 (en) | 1997-05-30 | 1998-05-29 | Satellite broadcasting system and broadcasting satellite |
Country Status (8)
Country | Link |
---|---|
US (1) | US6501938B1 (en) |
EP (1) | EP0984569A1 (en) |
JP (1) | JPH10336145A (en) |
KR (1) | KR20010013146A (en) |
CN (1) | CN1262002A (en) |
AU (1) | AU720781B2 (en) |
CA (1) | CA2291018C (en) |
WO (1) | WO1998054852A1 (en) |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6650868B1 (en) * | 1997-02-12 | 2003-11-18 | Ericsson, Inc. | Mobile satellite phone system incorporating symmetrical and non-symmetrical waveform modes |
FR2795576B1 (en) * | 1999-06-28 | 2007-01-05 | Centre Nat Etd Spatiales | SYSTEM COMPRISING A RADIO FREQUENCY ANTENNA SATELLITE |
EP1134927B1 (en) * | 2000-03-17 | 2009-09-30 | Thales | Method and system for mapping channels into a convolutional encoded time division multiplex in the downlink |
JP3574057B2 (en) * | 2000-09-04 | 2004-10-06 | 三洋電機株式会社 | Wireless receiving system and method |
US7142809B1 (en) * | 2001-02-27 | 2006-11-28 | The Directv Group, Inc. | Device and method to locally fill gaps in spotbeam satellite systems with frequency re-use |
CN100413226C (en) * | 2002-04-09 | 2008-08-20 | 阿尔卡特公司 | System and method of real-time interconnection of element of area monitoring, measuring or data collecting system through direct digital satellite broadcast complex system |
US7123911B1 (en) * | 2002-08-08 | 2006-10-17 | Sprint Spectrum L.P. | Method and system of wireless signal repeating |
KR100452630B1 (en) * | 2002-11-22 | 2004-10-14 | 한국전자통신연구원 | Digital broadcasting apparatus and method using the multiple transmitter/receiver antenna |
JPWO2006057386A1 (en) * | 2004-11-29 | 2008-06-05 | 松下電器産業株式会社 | Digital broadcast receiver |
FR2904897B1 (en) * | 2006-08-10 | 2008-09-26 | Alcatel Sa | BROADBAND AMPLIFICATION DEVICE |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS539893B2 (en) | 1973-05-07 | 1978-04-10 | ||
JPS6072335A (en) * | 1983-09-28 | 1985-04-24 | Kokusai Denshin Denwa Co Ltd <Kdd> | Identifying system of satellite beam |
JPH02131035A (en) * | 1988-11-10 | 1990-05-18 | Nec Corp | Repeater for satellite-mounted communication |
JPH0756953B2 (en) * | 1989-07-19 | 1995-06-14 | 日本電気株式会社 | Mobile satellite communication system |
JPH04192731A (en) * | 1990-11-27 | 1992-07-10 | Toshiba Corp | Satellite video transmission system |
US5708679A (en) * | 1993-03-11 | 1998-01-13 | Southern California Edison Company | Hitless ultra small aperture terminal satellite communication network |
US5563609A (en) * | 1994-05-16 | 1996-10-08 | Hughes Electronics | Antenna system with plural beam sequential offset |
US5754942A (en) * | 1996-09-09 | 1998-05-19 | Hughes Electronics Corporation | Satellite power level monitoring system and method using digital signal processing |
US6011951A (en) * | 1997-08-22 | 2000-01-04 | Teledesic Llc | Technique for sharing radio frequency spectrum in multiple satellite communication systems |
US6434384B1 (en) * | 1997-10-17 | 2002-08-13 | The Boeing Company | Non-uniform multi-beam satellite communications system and method |
US6023242A (en) * | 1998-07-07 | 2000-02-08 | Northern Telecom Limited | Establishing communication with a satellite |
-
1997
- 1997-05-30 JP JP9141901A patent/JPH10336145A/en active Pending
-
1998
- 1998-05-29 AU AU74555/98A patent/AU720781B2/en not_active Ceased
- 1998-05-29 WO PCT/JP1998/002391 patent/WO1998054852A1/en not_active Application Discontinuation
- 1998-05-29 KR KR19997011129A patent/KR20010013146A/en active Search and Examination
- 1998-05-29 CN CN98806657A patent/CN1262002A/en active Pending
- 1998-05-29 US US09/424,255 patent/US6501938B1/en not_active Expired - Fee Related
- 1998-05-29 CA CA002291018A patent/CA2291018C/en not_active Expired - Fee Related
- 1998-05-29 EP EP98921890A patent/EP0984569A1/en not_active Withdrawn
Non-Patent Citations (1)
Title |
---|
See references of WO9854852A1 * |
Also Published As
Publication number | Publication date |
---|---|
KR20010013146A (en) | 2001-02-26 |
CA2291018A1 (en) | 1998-12-03 |
AU7455598A (en) | 1998-12-30 |
AU720781B2 (en) | 2000-06-15 |
US6501938B1 (en) | 2002-12-31 |
CA2291018C (en) | 2003-07-08 |
CN1262002A (en) | 2000-08-02 |
WO1998054852A1 (en) | 1998-12-03 |
JPH10336145A (en) | 1998-12-18 |
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